I recruited Tali a few days ago and didn't have any issues.It worked fine on my first playthrough as well. I have ME2 on steam, maybe its a glitch with Origin? 

I only ran into this a few times - I had a few drones (well hidden) left to kill.   Do a sweep up.

Those drones can be pretty hard to find sometimes. Maybe some of them might be still around somewhere in the map.

I don't know who you are or where you came from, you glorious angelic being. but you saved my game. bless you